﻿<p>A structural reaction is a structural activity that results from a
structural action imposed to a structural item or building element.  Examples are support reactions,
internal forces, and deflections.</p>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC2x2.
</blockquote>

<blockquote class="change-ifc2x4">
IFC4 CHANGE&nbsp; Inverse attribute <em>Causes</em> deleted; use <em>IfcRelAssignsToProduct</em> via <em>HasAssignments</em> instead.
</blockquote>

<p>Structural reactions are grouped into <em>IfcStructuralResultGroup</em>s via the inverse
relationship <em>HasAssignments</em> and an <em>IfcRelAssignsToGroup</em> relationship object.
<em>IfcStructuralResultGroup.ResultGroupFor</em> finally refers to the structural analysis model
in which the results occur.</p>

<p>It is furthermore possible to establish relationships between reactions in one analysis model
and actions which they cause in another analysis model.  For example, a support reaction from one
structural system may be taken over as a load onto another supporting structural system.  This is
expressed by means of the inverse relationship <em>HasAssignments</em> of the reaction and an
<em>IfcRelAssignsToProduct</em> relationship object.  <em>IfcRelAssignsToProduct.Name</em> is set to
'Causes' and <em>IfcRelAssignsToProduct.RelatingProduct</em> refers to an instance of a subtype of
<em>IfcStructuralAction</em>.</p>
